Hey! My son did this too a couple of months back. Had been potty trained for a long time with no issues and suddenly lots of wet accidents. My little one is also a September baby due to start school next year. We also took him to drs thinking urine infection but came back clear. But I think it was just changes in routine that had thrown him off. We have one of the seats you put ontop of the loo. But after use we would take it off and put it down by the side, but found when he was desperate he didn’t have time to do all that. So we made our spare loo his very own toilet. So nothing got moved it was accessible for him at all times and that helped. We also ordered a sticker reward chart from Amazon and once he’d got all the stickers he would get a little treat and that incentive really worked too! Have you had any changes at home? Decorating? Moving things around? New routine, childcare changes? All of the above can cause a little change in their habits! Hope it balances out! X
Also to add - I just found that sometimes my little one would just be so engrossed in whatever he was doing he’d genuinely forget. Or sometimes would be the case he’d hold it too long as he didn’t want to miss out on whatever was going on. But be rest assured it doesn’t last, and couple months on we aren’t having that issue anymore! Good luck x
Some children have regressions and they are perfectly fine. The advice is to be friendly and remind them that pee goes in the toilet and ask them every 30 mins like when you potty trained.